Conus (Leptoconus) murravianus (Tate, 1890)

Descrizione:

Shell narrowly biconical, more than twice as long as wide; spire scalar, gradually tapering to the cylindroid pullus of three and a-half smooth convex whorls. Spire-whorls six, suture concealed by reflection of their posterior margin, bluntly angled a little in front of the middle, the longer backward-sloping area slightly concave; ornamented with close-set sigmoid striae and obsolete spiral threads. The posterior-half of the first whorl is slightly costated. Body-whorl broadly lanceolate in outline and narrowly truncate at the front, roundly angular at the periphery with a concave shoulder, which is obsoletely lirate ; whole surface marked with fine sigmoidal growth-lines, and at the front by encircling ridges. Outer lip with a shallow, obliquely-cut, notch at the posterior angle, thence with a gentle outward curve to the middle, and more rapidly declining to the front ⁽¹⁾.

Dimensions. — Length, 61 ; greatest width, 26 ; length of aperture, 46.

Locality. — Calciferous sandstones of the River Murray Cliffs near Morgan.

This species comes near to C. gradatulus, Sow., and differs so far as one can judge by the figure, by the ante-medial position of the blunter keel on the spire-whorls.

---

Protoconch (Plate II. Pigs. 4a, b) composed of three smooth turns implanted obliquely with reference to the axis of succeeding whorls; the initial portion is exceedingly small in comparison with the anterior turns. These latter are depressed and deeply canaliculated. The shell proper has an elevated spire with six whorls, which are somewhat staged, slightly excavated ; and spiral lineations are not prominent, except towards the anterior half of the body-whorl. It is noteworthy that in the brephic stage the periphery of the body-whorl was obscurely crenulated, a character which disappeared, however, as the neanic period was reached. Aperture narrow, slightly expanded in front ; outer margin thin with a shallow posterior sinus. This species presents characters of no less than three subgenera: by its very elevated spire and the obscure crenulations it recalls Conospirus, which does not appear to stand on a very firm basis; its protoconch presents the features of Lithoconus as represented in the Australian Tertiary by C. dennanti and C. pullulescens ; but the general contour of the shell and the staged whorls reflect Leptoconus, to which subgenus the species is here referred. Specifically it has a near ally in C. brocchii, Bronn, of the Italian Pliocene ⁽²⁾.

Dimensions.—Length 41mm.; breadth 16 mm. Professor Tate records a length of 61 m ⁽²⁾.

Form, and Loc.— Eocene : River Murray cliffs, G. 9136. One specimen. Presented by William Evans, Esq. ⁽²⁾.

Conus murravianus ⁽²⁾

(Tate, 1890)

Conus murravianus^(1) Eocene ? - River Murray cliffs	Conus murravianus 4 Miles S of Morgan, South Australia. Middle Miocene, Cadel Formation Balcombian [Coll. Angus Hawke]

---

Conus gradatulus

Northern Agulhas Bank, RSA

mm. 40

---

Bibliografia Consultata

· (1) - Tate (1890) – “TRANSACTIONS AND PROCEEDINGS REPORT OF THE ROYAL SOCIETY Of SOUTH AUSTRALIA”: pag. 199

· (2) - CATALOGUE TERTIARY MOLLUSCAIN THE DEPARTMENT OF GEOLOGY BRITISH MUSEUM (NATURAL HISTOHY). PART I. THE AUSTEALASIA TERTIARY MOLLUSCA. GEOEGE F. HARRIS, F.G.S.